Suspended Sedimentation Responses of Coral Reefs, Artificial Reefs and Non-Reef Areas in Palk Bay Southeast coast of India

Abstract Sedimentation is a key stressor affecting coral reef health, yet comparative data on sediment dynamics across natural coral reefs, artificial reefs, and adjacent non-reef habitats remain limited for the southeast coast of India. This study examined suspended sedimentation rates, sediment grain size composition, and their ecological implications across coral reef, artificial reef, and non-reef habitats in Palk Bay, Rameswaram, over a 12-month period (August 2024–July 2025). Sediment traps were deployed monthly following English et al. (1997), and grain size fractions (sand, silt, clay) were analyzed in parallel. Overall mean sedimentation was significantly higher in the non-reef area (46.56 ± 13.37 mg cm⁻² day⁻¹) than in the artificial reef (37.89 ± 12.31 mg cm⁻² day⁻¹) or coral reef (35.62 ± 14.35 mg cm⁻² day⁻¹) (Kruskal-Wallis H = 14.92, p = 0.001; ANOVA F = 6.71, p = 0.002), while coral reef and artificial reef sites did not differ significantly from each other. Sedimentation showed clear seasonality linked to the southwest and northeast monsoons, with significant seasonal variation in the artificial reef (F = 7.37, p = 0.013) and non-reef (F = 9.69, p = 0.006) areas. Sand was the dominant grain size fraction across all habitats (72.5–73.9%), with no significant inter-area differences in grain size composition; however, sedimentation rate was significantly negatively correlation with sand content in the coral reef area alone (Spearman r = − 0.622, p = 0.031). Field observations linked sediment deposition to coral tissue stress, partial bleaching, and reduced photosynthetic potential in the natural reef, and to elevated turbidity and delayed biofouling colonisation on artificial reef modules. These findings indicate that habitat structure, rather than reef origin, is the primary determinant of sediment exposure in this system, and highlight the need for sediment-informed management strategies to protect coral health and guide the siting and design of future artificial reef installations in Palk Bay.